Humectant and tactile properties such as a soft feel on the skin and lips, and a smooth, easily spreadable texture are highly desirable in cosmetics. In stick products, such as lipstick, lip balm, stick deodorants and other similar cosmetics, a formulation providing a stable, rigid form, in addition to humectant and tactile properties, is highly desirable. These tactile properties are provided in conventional cosmetic compositions by hydrophobic ingredients such as waxes, oils and fats.
Improved humectant properties are provided by adding hydrophilic ingredients to the composition and forming a stable water-in-oil emulsion. The emulsion compositions known in the art suffer from several drawbacks including lack of emulsion stability, particularly in stick compositions and high ingredient costs (e.g., haluronic acid costs), particularly in cream, lotion and beauty soap compositions.
It has been discovered that cosmetic compositions containing certain enzymatically debranched starches are characterized by stability and excellent humectant and tactile properties. It has been discovered that oil-free lotions may be formulated with the enzymatically debranched starches. The enzymatically debranched starches have been characterized as having unique gelling, lubricating and film-forming properties in aqueous dispersion (U.S. Pat. No. 4,971,723, issued Nov. 20, 1990, to Chiu; and U.S. Pat. Nos. 4,886,678 to Chiu, et al., issued Dec. 12, 1989; and 4,937,091 to Zallie, et al., issued Jun. 26, 1990). U.S. Pat. No. 3,957,969 to Fujiyama, et al., issued May 18, 1976, discloses the use of various polyhydroxyl compounds, including starch, in cosmetic stick formulations. It now has been discovered that only enzymatically debranched starches, and not starches in general, are useful in cosmetic stick formulations.
Starch is a polysaccharide typically comprising a mixture of about 20-25% amylose and about 75-80% amylopectin which is organized into compact granular structures. Amylose is a linear polymer of D-anhydroglucose units which are linked by alpha-1,4-D-glucosidic bonds. Amylopectin is a large branched polymer of amylose chains linked by alpha-1,6-D-glucosidic bonds in a tree-like structure. Depending upon the variety of plant from which the starch is obtained, amylose ordinarily contains between 250 and 12,500 D-anhydroglucose units and amylopectin contains between 400,000 and 3,125,000 D-anhydroglucose units. As used herein, "short chain amylose" refers to linear polymers containing from about 15 to 65 anhydroglucose units linked by alpha-1,4-D-glucosidic bonds.
Enzymes, or mixtures of enzymes which saccharify and debranch starch, have been used in starch conversion processes for the commercial production of low molecular weight oligosaccharides and sugars, such as dextrose (glucose). Starch conversion is the degradation of starch to lower molecular weight components by treatment with acid, oxidizing agents, heat, alkali or alpha-amylase enzymes. Enzymatic conversion of starch typically involves preferential hydrolysis of the alpha-1,4-D-glucosidic bonds, and only limited, if any, hydrolysis of the alpha-1,6-D-glucosidic bonds.
Glucoamylase rapidly hydrolyzes alpha-1,4-D-glucosidic bonds and slowly hydrolyzes alpha-1,6-D-glucosidic bonds, releasing glucose. In contrast, a debranching enzyme, such as pullulanase or isoamylase, rapidly hydrolyzes only the alpha-1,6-D-glucosidic bonds, releasing short chain amylose.
Debranching enzymes (enzymes which release short chain amylose from starch) have been proposed for use in conjunction with glucoamylase and alpha-amylase to improve the efficiency of production of high dextrose syrups; in low calorie alcoholic beverage production to improve fermentability of branched starch fragments; in production of maltose from starch in conjunction with beta-amylase; in low DE maltodextrin (30-55 glucose units) production to induce proteins to aggregate in aqueous emulsions; and in enzymatic conversion of starch into a soluble syrup having a high quantity of disaccharides and trisaccharides. These debranching enzyme applications are directed to problems arising from the presence of branched starch or dextrin fragments following starch conversion processes. In each application, the debranching enzyme is employed in the complete conversion of starch to a variety of low molecular weight fragments such as sugars or maltodextrins. The thickening, adhesion and gelling characteristics of starch are lost.
The use of debranching enzymes to fully debranch starch, with hydrolysis of substantially all alpha-1,6-D-glucosidic bonds, so as to obtain pure, or amylopectin-free, low molecular weight amylose is taught in U.S. Pat. No. 3,730,840 to Sugimoto, et al.; U.S. Pat. No. 3,881,991 to Kurimoto, et al.; and U.S. Pat. No. 3,879,212 to Yoshida. The object of these patents is to produce pure short chain amylose. The presence of any residual amylopectin is taught to be objectionable. No disclosure is made of any lubricating or humectant properties or utilities within the field of cosmetics formulation.
Thus, the background of enzyme-related starch technology does not suggest that starches useful as ingredients in cosmetic compositions may be prepared by employing debranching enzymes to debranch the amylopectin component of starch, yielding short chain amylose, and, optionally, partially debranched amylopectin, native amylose, or amylopectin, with or without substantial conversion of the starch. These starches and the enzymatic process offer significant advantages over other products and processes in cosmetics where "natural" and "hypoallergenic" claims frequently appear in product marketing programs.